Add diagnostic query to get correctly extracted files

Author: tamasvajk

csharp/ql/src/Diagnostics/DiagnosticNoExtractionErrors.ql

@@ -0,0 +1,14 @@
+/**
+ * @name Successfully extracted files
+ * @description A list of all files in the source code directory that were extracted
+ *              without encountering an extraction error in the file.
+ * @kind diagnostic
+ * @id cs/diagnostics/successfully-extracted-files
+ */
+
+import csharp
+import semmle.code.csharp.commons.Diagnostics
+
+from File file
+where file.fromSource() and not exists(ExtractorError e | e.getLocation().getFile() = file)
+select file, ""

csharp/ql/test/library-tests/diagnostics/A.cs

@@ -0,0 +1,4 @@
+public class A
+{
+    public void M() { }
+}

csharp/ql/test/library-tests/diagnostics/DiagnosticNoExtractorErrors.expected

@@ -0,0 +1 @@
+| A.cs:0:0:0:0 | A.cs |  |

csharp/ql/test/library-tests/diagnostics/DiagnosticNoExtractorErrors.qlref

@@ -0,0 +1 @@
+Diagnostics/DiagnosticNoExtractionErrors.ql